The invention relates to an automatic coffee machine, in particular for the preparation of individual cups and small pots, with an instantaneous water heater for the preparation of hot water integrated into the housing, with a device for the feeding of coffee powder, with a brewing device having a brewing chamber which consists of a stationary tube section with a vertical axis and two locking pieces, located at least partly in the instantaneous water heater, with at least a part of the tube section of the brewing chamber being surrounded by the hot water of the instantaneous water heater, and with axial drive for the moving of the upper locking piece toward the axis of the tube section and a radial drive for the radial motion in relation to the this axis.
An automatic coffee machine is usually considered as being automatic when the processes of grinding the coffee powder, feeding the coffee powder into the brewing chamber, the brewing process itself and the ejection of the lixiviated coffee powder and the pushing-out of the lixiviated and dry-pressed coffee powder tablet are done automatically, without one of these or other procedural steps having to be carried out or assisted manually. Yet, it is understood that for the effectuation of a cyclic process the automatic coffee machine needs to be actuated by the pressing of a switch, etc. The invention can also be applied to an automatic quantity fresh-brewing device.
A coffee machine of the type described at the outset is known from the U.S. Pat. No. 2,827,845. It has the important advantage that the vertically located brewing chamber formed by a single tube section is already at least partly situated in the housing of the instantaneous water heater so that, regardless of the chronological sequence of the brewing cycles, a largely constant outflow temperature of the coffee beverage will be attained. Hence, the brewing frequency does not influence the outflow temperature. In this case, the brewing device is already equipped with an upper locking piece located in such a way that it can travel both radially and axially in relation to the axis of the brewing chamber tube section. The locking piece itself has conical shape and is equipped with a gasket, having merely the function of sealing the brewing chamber on the top. The capacity for radial traveling can be used to the advantage of having easy access to the brewing chamber at the top for the feeding of coffee powder, and that the coffee grinder can be installed as stationary device above this opening. The brewing chamber also includes a lower locking piece swinging around a horizontal axis, also conical and equipped with a gasket. In the area of the lower locking piece, there is also the hot water inlet into the brewing chamber. In this context, the feeding of hot water does not cause any problems, i.e. neither in the lower ranges of the tube section, nor around the upper locking piece. However, such a brewing chamber with conical locking pieces has the disadvantage that it is impossible to move these conical locking pieces in the tube section in the way of a piston and for example to pre-press the loosely fed coffee powder into a tablet, which would bring about the benefit of a better and more even utilization of the coffee powder. It is also impossible to re-press or dry-press such a tablet after it is lixiviated, and thereby effectuating a dry ejection.
Another automatic coffee machine is known from WO 82/01120. There, the brewing chamber consisting out of a stationary tube section with vertical axis is designed with a carrier plate, linked through a structure of motion links to a second carrier plate. In the second carrier plate, there are hydraulic cylinder/piston-units by means of which two piston-like locking pieces at each end of the tube section may travel into or be moved within the tube section. While the lower locking piece is actuated directly through the pertinent piston/cylinder-unit, the force for the upper locking piece is detoured by way of a yoke-like structure. Both locking pieces are only axially moveable. In addition there is a swivelling funnel piece serving the purpose of feeding the coffee powder from the side into the brewing chamber and the disposing of the lixiviated coffee powder tablet from the brewing chamber. Therefore the coffee grinder is located outside the axis of the brewing chamber so that the funnel piece in its swung-out position may be filled by way of the mill. Regardless of the fact that this construction of the brewing chamber is very costly, another disadvantage is that the upper locking piece with its gasket has to be moved through the swivelling funnel piece, which causes the gasket to travel in and out at the edge of the vertical tube section. This shortens the life of the gasket and thus the perfect functioning of such a coffee machine considerably. Nevertheless, also in this case, the upper locking piece is designed as one part so that in the area of the upper locking piece the feeding of the hot water may be carried out without problems. However, the locking piece cannot be subject to any centering action. Rather, a precise guiding mechanism for the motion links is necessary in order to maintain the function of the gasket at least throughout a relatively short period of time.
CH-PS 597 812 discloses that the upper locking piece of a brewing chamber should be designed in two parts and that the hot water should also be fed into the brewing chamber in the area of this locking piece. There are also meant to be two gaskets of which one gasket is responsible for the sealing of the brewing chamber to the outside, whereas the other gasket seals the hot-water inlet into the brewing chamber. Here, this upper locking piece is traveling radially to the vertical axis of the brewing chamber, while for the purpose of traveling only the gasket that is pressed down inversely, when hot water is let into the brewing chamber, is relieved of the pressure. In the case of radial traveling of the upper locking piece, however, the disengaged gasket rubs over a certain surface in an adverse way, which results in a certain degree of wear.
The EP 100 030 A2 shows a coffee machine with radial powder feed, with the upper locking piece being devised as merely axially traveling in the axis of the tube section of the brewing chamber. Also in this case, gaskets are traveling across edges in an adverse way, which naturally shortens the life of these gaskets. Also DE 36 15 158 C1 shows a coffee machine, where a tube section with vertical axis forms an essential component of the brewing device. It includes an upper locking piece that together with its gasket enters the tube section and travels out of it again. This upper locking piece is devised as one single part and thus permits the feeding of hot water without problems. The lower locking piece is meant to swivel in order to facilitate the downward ejection of the coffee powder. When swung out radially, the surface rubs on the gasket of the lower locking piece, which results in a certain wear. Since this is the case for the lower area of the brewing chamber, the brewed coffee drips out in a downward direction. The entry and the crossing of edges of the tube section also leads to sealing problems in the upper part.